1. Field of the Invention
The present invention relates to an image processing method capable of properly recognizing the road condition ahead, especially a vehicle or like object ahead, by processing an image captured by a camera mounted on a vehicle.
2. Description of the Related Art
In the conventional art, it is practiced to recognize a vehicle, or like object, ahead or make range measurements, etc. using an image captured by a camera. In this case, to recognize the vehicle or like object ahead, edge extraction is performed to obtain an edge image and, based on the obtained edge image, the range and angle to the vehicle or like object ahead are measured. Refer, for example, to Japanese Unexamined Patent Publication No. 2001-101428.
An edge is a contour line where the gray level of the image changes rapidly, and the advantage is that an edge remains relatively unaffected if the gray level changes due to a shadow or stain. In edge extraction, either vertical or horizontal edges, or both vertical and horizontal edges, can be extracted.
When performing edge detection in image processing, either vertical or horizontal edges, or both vertical and horizontal edges, are detected using, for example, cameras arranged on the left and the right, and the range and angle to the target object are measured. However, depending on camera noise or surrounding conditions, edges may not appear at constant positions and, when detecting edges at predetermined intervals of time, it is often not possible to detect edges consistently. For example, an edge of a particular portion of a vehicle traveling ahead may not appear at a certain instant in time or may not appear at a constant position, making it impossible to consistently detect the edge of that portion.
It is accordingly an object of the present invention to provide an image processing method that can compensate for such inconsistent edge detection.